The Sudden Infant Death Syndrome (SIDS) remains a leading cause of infant deaths inspite of recent highly successful public health interventions designed to reduce SIDS risks (The U.S. "Back to Sleep" campaign, "BTS"). We propose to study several physiologic and neuro-developmental mechanisms potentially involved in the etiology of SIDS, as well as, pertinent environmental factors. The research will focus on three areas. In the first of these, we plan to study the physiology of recovery from severe hypoxia by gasping (autoresuscitation, AR). These studies will determine if the previously documented developmentally acquired defect in AR, originally described in SWR mice, is present in other inbred strains and species and, furthermore, if underlying mechanisms causing AR failure are similar to those in SWR mice. Additionally, the effects of increased environmental temperature on AR will be evaluated. Also, Home apnea monitor recordings of infants dying suddenly and unexpectedly while being monitored will be studied to determine if there is evidence of attempted AR and if so, potential reasons for its failure. The second part of our studies will be directed to prospectively obtaining data on the case history, death scene and postmortem examination of infant's dying with the diagnoses of SIDS, accidental suffocation and "cause of death undetermined" in the St. Louis metropolitan area. The aim is to determine how many of these deaths are preventable by public acceptance of current "BTS" guidelines and how many might be prevented by future additions or changes in the recommendations to child caretakers. In connection with this study, we will perform special death scene investigations in certain SIDS and accidental suffocation deaths combined with laboratory death scene reconstruction studies in order to determine if additional simple guidelines for parents and child equipment manufactures can be formulated in order to prevent infant deaths. Finally, we will study development of the infant's ability to avoid potentially suffocating environments during sleep, and determine the potential role of the infant's past experience on this development.